Underground Into Adventure
by GoldGuardian2418
Summary: The Knights ambush Rook, Summer, and Forrest and Summer gets transported to Snowdin in the now-empty Underground. Will she find her way back? Done as a request for VinnieStokerLover. :)


**VinnieStokerLover, who owns Summer and Forrest, asked for this one. Here you go, Amiga! Enjoy! :)**

 **Ben 10 belongs to Cartoon Network and Man of Action. Undertale belongs to Toby Fox. I only own Rachel and Courtney.**

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 **Underground Into Adventure**

"Okay, we got the camping gear. Honey, do you have protective shields?" Rachel asked.

"Several of them, my love," Rook said with a smile as he hugged her. "Are you sure you don't wish to come with us?"

"I've got those big contracts coming up, Rook," the woman said gently. "Besides, Courtney's still settling in. For both you and me to be gone right now would make her uneasy."

"You're right, Baby," he said and pulled her into a loving kiss that she melted into, smiling at him after they parted. "I'll miss you."

"And I'll miss you, Summer, and Forrest," she said just as their two youngest children came downstairs with Courtney helping carrying their duffel bags while they carried their sleeping bags. As Rook loaded their stuff in his Proto-Truk, Courtney turned to Rachel.

"Mom, are you sure Summer and Forrest will be okay?" She asked. "I mean, I know Dad will be there, but…,"

The older woman knew the eleven-year-old was just being cautious. "They'll be fine, sweetie," she said with a smile. "You could go with them, if you'd like."

Courtney shook her head. "No, I'm good," she said. "I don't really like camping."

Rachel looked at her, concerned. "Bad memories?" She asked gently.

The girl nodded. "My parents sent me to camp when I was little, before they died," she said. "The other campers were mean to me. They put a garter snake in my bed and locked me out of the cabin once and I had to go get the camp counselor, who didn't believe me that the others had locked me out."

The older woman took her daughter into her arms. "Oh, sweetie," she said sympathetically. "Well, sometime when I'm free from work, all of us will go camping and make it a much better memory for you."

Courtney looked at her. "Just you, me, Dad, Summer, and Forrest?" She asked.

"Just the five of us," Rachel promised as Rook came back in and the younger children hugged their mother and older sister. "You two have fun and mind your father," she said to them.

"Yes, Mommy," Summer said.

"Yes, Mom," Forrest said.

Rook hugged his older daughter. "Be good for your mother, sweetheart," he said.

"Yes, Dad," Courtney said.

Rachel hugged her fiancée and gave him a quick kiss on the mouth. "We'll be fine, honey," she said, making him smile at her before he and the younger children headed out to the campsite he had selected.

Before they set up for camp, Rook put on his I.D. Mask and stopped for some more dried fruits and other supplies with the children staying beside him, but when they were about ready to go, Rook noticed a target beam on Summer's shirt and he looked up to see the Forever Knights taking aim. "Summer! Forrest! Get down!" He said urgently.

The children quickly ducked and Forrest went to crawl under the Proto-Truk and he went to grab Summer's hand as she reached for him, but just then, a beam of light hit Summer and she vanished. "NO!" Rook screamed.

"Summer!" Forrest cried out.

Rook angrily turned to the Knights. "Forrest, get in the truck," he said and the little boy instantly did so as Rook pulled out his Proto-Tool and took off his I.D. Mask to reveal his angry face to the Knights. "As my fiancée would say, you made a very big mistake."

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Summer felt something cold stop her fall and she got up, finding it to be snow and she shivered as the cold wind hit her unprotected arms and face. Her t-shirt, jeans, and sneakers did nothing to keep the cold away and she glanced around. "Where am I?" She asked herself before remembering that moving around would help her blood continue flowing through her body and she began moving, shivering more as she continued walking.

She didn't have to go too far when she heard something approaching fast and it scared her to where she dove behind a snow bank, but the footsteps stopped nearby. "Summer? Is that you, kiddo?" Asked a familiar voice.

The five-year-old lifted her head up at that and her eyes lit up gratefully at seeing Sans and Gaster standing there. "Uncle Sans! Uncle Gaster!" She said, jumping up and tripping, but Sans caught her and pulled her into a hug.

"Oh, my word, kid, you're freezing," the shorter skeleton said and quickly took off his hoodie, wrapping it around Summer. Gaster took one of the little girl's hands and noticed how cold it was.

"She's too cold," he said and lifted both his younger brother and the girl in his arms. "Sans, Grillby's old restaurant."

Sans didn't argue and teleported them there. Grillby was in the old restaurant as he had come down to make sure he hadn't forgotten anything when he moved his business up to the surface and he whirled around in surprise at hearing the familiar sound of teleporting and was more shocked when he recognized the little girl in Sans' arms. "Summer?" He asked in worry.

"Grillbz, she landed in Snowdin," the short skeleton said urgently.

Immediately, the fire elemental took the small girl from his friend and held her, placing her head right under his chin as his body temperature increased a few degrees. Summer shivered a bit as she clung to him and snuggled into the bartender, who continued to hold her until Gaster again took the little girl's hand and nodded as the child was now out of danger of catching a cold. "How did you get here, Summer?" Grillby asked. "Mt. Ebbot is far away from Staybrook."

"Daddy, Forrest, and I were going camping and the Forever Knights showed up and a line of light hit me and I was here," she said.

"Sounds like a transport beam," Sans said as he pulled out his phone and texted Rook to let him know Summer was safe.

The little girl looked out the window. "Is this Snowdin, where you guys came from?" She asked.

"Yep, part of the Underground, kiddo," the joke-loving skeleton said. "It's dead right now since everyone moved to the surface, but we occasionally come back to make sure we didn't leave anything behind."

Summer reached for Sans and Grillby handed her over to the skeleton, who took her in his arms and she hugged him. "I'm glad you guys are here," she said with a small whimper.

"Believe me, kid, I'm glad we were too," he said before looking at his brother and friend. "Gaster, why don't you transport Grillbz back to the surface and I'll get Summer back to Rook."

They nodded and Summer reached for them, hugging them. "Love you, Uncle Gaster," she said to the taller skeleton, who chuckled and nuzzled her nose gently with his own nose bone in affection before handing her to Grillby and the little girl hugged the fire elemental. "Love you, Uncle Grillby," she said.

He also chuckled and nuzzled her cheek with his cheek, making her giggle before she was handed back to Sans and the short skeleton snapped his fingers, teleporting to the campsite Rook had picked out, making the Revonnahgander jump and grab his weapon while putting Forrest behind him, but the alien relaxed at seeing his friend and daughter. "Summer," he said, accepting her from Sans.

"Daddy!" She said, hugging him hard.

Sans nodded. "I'm going to talk to the Plumbers you're a part of, Rook," he said. "The Underground is empty and if the Forever Knights are sending the kids there, none of us would know unless we were down there."

Rook nodded. "Yes," he said. "Thank goodness you were there. I got your text message."

The skeleton nodded and saw Summer take off the blue hoodie and hand it back to him. "You warm enough now, kiddo?" He asked. "Your dad and your mother won't be happy with me if you get sick."

"I'm good, Uncle Sans," she said.

Rook smiled. "Sans, do you and your brothers want to join us?" He offered.

"Love to, but Papyrus' big cooking test is coming up tonight and Gaster is presenting one of his and Alphys' projects at a convention day after tomorrow," Sans said, a note of regret in his voice.

"Well, you all are welcomed to come to the mansion afterwards," Rook said.

"Thanks, Rook," said Sans before teleporting away and Rook looked at his daughter, who saw the campfire was going.

"Daddy, can we make s'mores after dinner?" She asked.

"That sounds good," he said as the three of them continued to set up camp, the kids ready to enjoy camping with their father.

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 **GoldGuardian2418**


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